1. Field of the Invention
The invention generally relates to electromagnetic relays and to contact systems therefore and, in particular, to electromagnetic relays for switching multiple contacts.
2. Description of the Related Art
Presently, several techniques have been developed for electromagnetic relays, which are generally adopted to close or open one or more electric circuits by means of electric control voltages and are used in the following application areas:                switching of high power controlled by low power,        separating different voltage levels, for instance low voltage at the input side and mains voltage at the output side,        separating DC and AC circuits,        simultaneous switching of several circuits by means of one single control signal,        linking of information and thereby building up control sequences.        
In particular, in the area of automotive electronics, relays are used for various switching tasks. The efforts of the automobile industry to replace conventional systems, as for instance the hydraulic steering support, by electric systems, require switches, which can switch off the employed three phase motors in case of a failure securely. A such like switch for disconnecting and connecting a star point of a three phase motor (e.g. For 12 V and 42 V on-board supply systems in a current range of more than 40 A and 15 A, respectively) can conventionally be realized by means of conventional relays, as shown schematically in the FIGS. 8 to 10 by interconnecting one form-U relay (FIG. 9) or two form-A (FIG. 8) or form-X contact pairs (FIG. 10). This nomenclature is in accordance with the symbols of the American National Standard Institute, ANSI. Known electromagnetic relays which have contact bridges with two movable contacts each, are disclosed for instance in the U.S. Pat. No. 5,151,675 (Bier et al.) And U.S. Pat. No. 4,540,963 (Ester et al.).
However, because the dissipation power augments with the square of the current, with such conventional realizations, wherein normally open contacts with a center tap, or different normally open relays are interconnected, occur unduly high dissipation power values. A use of conventional high current relays, however, involves the disadvantage of significantly higher costs, size and weight.